Dynamic Pumping Characteristics of the Hemopump®

Abstract

While pumping blood with the Hemopump® in sheep, the ability of predicting the instantaneous pump flow from the pressure difference over the pump system and pump parameters was investigated. For rotational speed n between 300 and 475 revolutions per second (rps), maximum pump flow Q_O(n) at zero pressure difference, internal pump resistance R(n), and inertia parameter L_c were found to be suitable parameters for Hemopump® characterization. The instantaneous pump flow could be estimated with an accuracy of approximately 1.0 [ml/s]. The values of the pump source parameters (± sd) were: (the figures in parentheses represent earlier reported values found while pumping water) L_c was a constant of 21.4 ± 6.4 [Pa·s²/ml] (in water: 10.8). Q_O(n) is linearly related to rotational speed n according to: Q_O(n) = Q_o(n_cen) + C_Q(n - n_cen), with Q_O(n_cen) = 49.4 ± 4.5 [ml/s] (in water: 60.3), C_Q = 142 ± 22.4 [10⁻³ ml] (in water: 146), and n_cen = 387.5 [rps]. R(n) is linearly related to rotational speed n according to: R(n) = R(n_cen) + C_R(n - n_cen), with R(n_cen) = 556 ± 124 [Pa·s/ml] (in water: 502) and C_R = 1.47 ± 0.83 [Pa·s²/ml] (in water: 1.67).